The eight-piece roof opened in eight minutes and 10 seconds, beating the 12-minute maximum that architects and the Falcons organization had long promised. The roof then was reclosed in just over seven minutes.

The demonstration before a gathering of media members marked what stadium officials called the finish of construction on the roof, 11 months after the $1.5 billion-plus venue hosted its first event.

“It’s great to have it finished,” said Mike Egan, a senior vice president of Falcons and Atlanta United parent company AMB Group. “It was never a question of the roof being broken or unsafe. It was literally just a question of needing to get the balance (of the roof) right so the propulsion system would achieve its desired life.

“It took as long as it did because this is a busy building and we had to work around events,” added Egan, who has executive oversight of the stadium project. “It’s a relief, but we really never had any doubt we would get to this point. It’s more just a feeling of exhilaration to see it working the way it is supposed to.”

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The Falcons plan to hold a public roof-opening ceremony before a team practice in the stadium Sunday.

The complicated roof caused construction delays and cost overruns when the stadium was being built and wasn’t fully automated when the stadium debuted last August. The roof has been open for only three major events to this point – one Falcons game and two Atlanta United matches – and until recently it hadn’t operated with the designed speed or efficiency. Compounding the issues, the closed roof leaked during several events, including during warmups for the college football national championship game in January.

But stadium officials now say they have moved past all of that, with AMB Group CEO Steve Cannon describing the roof as “fully functioning.”

It performed as designed during the demonstration Wednesday, opening smoothly from the center to reveal the sky.

Mark Silvera, of Uni-Systems Engineering, which designed and supplied the mechanization equipment for the roof, said the stadium will be able to routinely open the roof in eight minutes without putting undue wear on the propulsion system.

“That’s what we designed it for,” Silvera said.

The roof closes in about one minute less than it opens because it reaches full speed faster on closing, Silvera said.

Each of the roof’s eight triangular steel pieces, called petals, measures more than 200 feet long, weighs more than 500 tons and moves in straight lines along separate tracks. Each petal rests on eight bogies, which are two-wheeled mechanisms that sit on the track rails. When the roof is opened or closed, the motorized petals move along the tracks, which are attached to the 18,000-ton fixed portion of the roof. The petals cantilever over the field when the roof is in the closed position.

The key to getting the roof to work as designed “was maintaining an even distribution of petal weight across the rails,” Egan said. “The petals were overly stiff as initially built, which ... put too much drag on the propulsion system.”

Going forward, it will be interesting to see how often the roof is open for Falcons and Atlanta United games. The teams’ owner, Arthur Blank, and other officials have said they plan to play more games with the roof open than closed.

That would buck the trend of the four other NFL teams with retractable-roof stadiums. Collectively, the Arizona Cardinals, Dallas Cowboys, Houston Texans and Indianapolis Colts have chosen to play with their roofs open in only about one-third of the games.

Egan said the Falcons will open their roof more often than those teams because “we built an outdoor stadium and put a roof on it.”

“That allows us to open the roof if there is a 25-percent chance of precipitation because we have drainage and because everything in this stadium is designed to get wet,” Egan said. “We’re going to open it as much as we can. Fan comfort will be the No. 1 priority.”

The NFL has said it would like to play Super Bowl LIII, which will be in Mercedes-Benz Stadium on Feb. 3, with the roof open if the weather is favorable – a big if, of course.